Article

To the Editor,

Although it is difficult to briefly review the most important implantable cardioverter defibrillator (ICD)-related developments from the last year (since September 2015), we consider it important to offer an outline of the articles we believe to be the most relevant for clinicians working in this field, while acknowledging that some important findings will be omitted.

The DANISH trial1 addressed the use of ICDs in primary prevention in patients with nonischemic dilated cardiomyopathy. In this population, although ICDs are a class I indication in clinical guidelines, there is still no solid evidence for their use because no major study has examined the usefulness of these devices in this specific patient group. The DANISH study included 1116 patients with nonischemic dilated cardiomyopathy in New York Heart Association functional class II-IV receiving standard treatment for heart failure. These patients were randomized 1:1 to an ICD implant or usual clinical care. In both groups, 58% of patients underwent cardiac resynchronization therapy. After a median follow-up of 67.6 months, there were no differences in death from any cause or death from cardiovascular causes. However, there was a reduction in sudden cardiac death in ICD patients (hazard ratio [HR], 0.5; 95% confidence interval, 0.31-0.82; P = .005). ICDs had no benefit in patients undergoing cardiac resynchronization therapy. Although the data indicate that ICDs had a beneficial effect on total mortality in younger patients (less than 68 years), the difference was not statistically significant.

On the other hand, the work of Roth et al.2 highlighted the benefits of drug optimization for heart failure by showing that patients with dilated cardiomyopathy who received guideline-directed medical therapy before ICD implantation have a lower mortality rate 1 year after ICD implantation (11.1% vs 16.2%).

Regarding ICD implantation, the results of the NORDIC ICD study,3 with 1077 patients randomized to defibrillation testing at the time of ICD implantation, concur with those of previous studies reporting that systematic testing is not necessary.

A notable consensus statement on ICD programming was published by the 4 continental electrophysiology societies.4 Numerous optimal programming-related recommendations were made, and the document particularly stressed ways to reduce inappropriate and unnecessary therapies, such as a prolonged detection duration for ventricular arrhythmia, an increased rate cutoff for ventricular tachycardia/ventricular fibrillation (VF), programming of more than 1 zone, and the use of discriminators for supraventricular tachycardia.

Regarding ICD follow-up, a Spanish multicenter observational study5 that included 2507 consecutive patients used remote monitoring (CareLink, Medtronic) to analyze the baseline R wave amplitude and its relationship with R wave amplitude during VF detection. An R wave ≥ 5 mV seemed to be sufficient to ensure a rapid and accurate sensing of VF. In contrast, a median amplitude of ≤ 2.5 mV (interquartile range, 2.3-2.8 mV) could lead to at least a 25% rate of undersensed R waves during a VF episode. These data might be of interest in the follow-up of patients, when changes are being considered in the defibrillation lead at the time of generator replacement, and when defibrillation testing is planned in patients at high risk of complications.

Finally, it is important to highlight the work of Akar et al.6 into remote monitoring because their results show that remote monitoring of ICDs is associated with a reduction in death from any cause and rehospitalizations. They analyzed the data of patients with an ICD, comparing patients with and without remote monitoring. A total of 37 742 patients were included in the mortality analysis and 15 254 in the readmission analysis. About 66% of the patients were at least 40 km from the implanting facility. The results found that remote monitoring was associated with a lower risk of death at 3 years (HR, 0.67; 95%CI, 0.64-0.71; P < .0001) and readmission for any cause (HR, 0.82; 95% CI, 0.80-0.84; P < .0001). These data once again show that the use of this technology should be expanded.